[Improve file explorer & implement Assimp with lighting/material support]

- Reworked file explorer UI for clearer hierarchy and usability
- Actually wired up Assimp properly for model loading
- Added basic lighting support
- Added independent material support per mesh
(oh my gosh this took 4 days to actually get working, let alone not crashing 😭)

Resources/Shaders/frag.glsl

@@ -6,41 +6,101 @@ in vec3 Normal;
 in vec2 TexCoord;
 
 uniform sampler2D texture1;
-uniform sampler2D texture2;
+uniform sampler2D overlayTex;
+uniform sampler2D normalMap;
 uniform float mixAmount = 0.2;
+uniform bool hasOverlay = false;
+uniform bool hasNormalMap = false;
 
-uniform vec3 lightPos;
 uniform vec3 viewPos;
-uniform vec3 lightColor = vec3(1.0);
+uniform vec3 materialColor = vec3(1.0);
 
 uniform float ambientStrength = 0.2;
 uniform float specularStrength = 0.5;
 uniform float shininess = 32.0;
+const int MAX_LIGHTS = 10;
+uniform int lightCount = 0; // up to MAX_LIGHTS
+// type: 0 dir, 1 point, 2 spot
+uniform int lightTypeArr[MAX_LIGHTS];
+uniform vec3 lightDirArr[MAX_LIGHTS];
+uniform vec3 lightPosArr[MAX_LIGHTS];
+uniform vec3 lightColorArr[MAX_LIGHTS];
+uniform float lightIntensityArr[MAX_LIGHTS];
+uniform float lightRangeArr[MAX_LIGHTS];
+uniform float lightInnerCosArr[MAX_LIGHTS];
+uniform float lightOuterCosArr[MAX_LIGHTS];
+
+// Single directional light controlled by hierarchy (fallback if none set)
+uniform vec3 lightDir = normalize(vec3(0.3, 1.0, 0.5));
+uniform vec3 lightColor = vec3(1.0);
+uniform float lightIntensity = 1.0;
 
 void main()
 {
     vec3 norm = normalize(Normal);
-    vec3 lightDir = normalize(lightPos - FragPos);
     vec3 viewDir = normalize(viewPos - FragPos);
 
-    // Ambient
-    vec3 ambient = ambientStrength * lightColor;
-
-    // Diffuse
-    float diff = max(dot(norm, lightDir), 0.0);
-    vec3 diffuse = diff * lightColor;
-
-    // Specular (Blinn-Phong)
-    vec3 halfwayDir = normalize(lightDir + viewDir);
-    float spec = pow(max(dot(norm, halfwayDir), 0.0), shininess);
-    vec3 specular = specularStrength * spec * lightColor;
-
     // Texture mixing (corrected)
     vec4 tex1 = texture(texture1, TexCoord);
-    vec4 tex2 = texture(texture2, TexCoord);
-    vec4 mixedTex = mix(tex1, tex2, mixAmount);
-    vec3 texColor = mixedTex.rgb;
+    vec3 texColor = tex1.rgb;
+    if (hasOverlay) {
+        vec3 overlay = texture(overlayTex, TexCoord).rgb;
+        texColor = mix(texColor, overlay, mixAmount);
+    }
+    vec3 baseColor = texColor * materialColor;
 
-    vec3 result = (ambient + diffuse + specular) * texColor;
-    FragColor = vec4(result, mixedTex.a);  // Preserve alpha if needed
-}
+    // Normal map (tangent-space)
+    if (hasNormalMap) {
+        vec3 mapN = texture(normalMap, TexCoord).xyz * 2.0 - 1.0;
+        vec3 dp1 = dFdx(FragPos);
+        vec3 dp2 = dFdy(FragPos);
+        vec2 duv1 = dFdx(TexCoord);
+        vec2 duv2 = dFdy(TexCoord);
+        vec3 tangent = normalize(dp1 * duv2.y - dp2 * duv1.y);
+        vec3 bitangent = normalize(-dp1 * duv2.x + dp2 * duv1.x);
+        mat3 TBN = mat3(tangent, bitangent, normalize(Normal));
+        norm = normalize(TBN * mapN);
+    }
+
+    vec3 ambient = ambientStrength * baseColor;
+    vec3 lighting = ambient;
+
+    int count = min(lightCount, MAX_LIGHTS);
+    for (int i = 0; i < count; ++i) {
+        int ltype = lightTypeArr[i];
+        vec3 ldir = (ltype == 0) ? -normalize(lightDirArr[i]) : lightPosArr[i] - FragPos;
+        float dist = length(ldir);
+        vec3 lDirN = normalize(ldir);
+
+        float attenuation = 1.0;
+        if (ltype != 0) {
+            float range = lightRangeArr[i];
+            if (range > 0.0 && dist > range) continue;
+            if (range > 0.0) {
+                float falloff = clamp(1.0 - (dist / range), 0.0, 1.0);
+                attenuation = falloff * falloff;
+            }
+        }
+
+        float intensity = lightIntensityArr[i];
+        if (intensity <= 0.0) continue;
+
+        float diff = max(dot(norm, lDirN), 0.0);
+        vec3 diffuse = diff * lightColorArr[i] * intensity;
+
+        vec3 halfwayDir = normalize(lDirN + viewDir);
+        float spec = pow(max(dot(norm, halfwayDir), 0.0), shininess);
+        vec3 specular = specularStrength * spec * lightColorArr[i] * intensity;
+
+        if (ltype == 2) {
+            float cosTheta = dot(-lDirN, normalize(lightDirArr[i]));
+            float spotAtten = smoothstep(lightOuterCosArr[i], lightInnerCosArr[i], cosTheta);
+            attenuation *= spotAtten;
+        }
+
+        lighting += attenuation * (diffuse + specular) * baseColor;
+    }
+
+    float alpha = tex1.a;
+    FragColor = vec4(lighting, alpha);  // Preserve alpha if needed
+}